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   "source": [
    "**交换数组arr中的列1和列3。**\n",
    "\n",
    "- `arr = np.arange(9).reshape(3, 3)`\n",
    "\n",
    "【知识点：索引与切片】\n",
    "- 如何交换二维数组中的两列？"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "metadata": {
    "ExecuteTime": {
     "end_time": "2020-09-06T02:56:51.266868Z",
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    }
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "[[0 1 2]\n",
      " [3 4 5]\n",
      " [6 7 8]]\n",
      "[[2 1 0]\n",
      " [5 4 3]\n",
      " [8 7 6]]\n"
     ]
    }
   ],
   "source": [
    "import numpy as np\n",
    "\n",
    "arr = np.arange(9).reshape(3, 3)\n",
    "print(arr)\n",
    "# [[0 1 2]\n",
    "#  [3 4 5]\n",
    "#  [6 7 8]]\n",
    "\n",
    "x = arr[:, [2, 1, 0]]\n",
    "print(x)\n",
    "# [[2 1 0]\n",
    "#  [5 4 3]\n",
    "#  [8 7 6]]"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "ExecuteTime": {
     "end_time": "2020-09-06T02:57:26.869431Z",
     "start_time": "2020-09-06T02:57:26.864408Z"
    }
   },
   "source": [
    "**交换数组arr中的第1行和第2行。**\n",
    "- `arr = np.arange(9).reshape(3, 3)`\n",
    "\n",
    "【知识点：索引与切片】\n",
    "- 如何交换二维数组中的两行？"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "metadata": {
    "ExecuteTime": {
     "end_time": "2020-09-06T02:57:43.336029Z",
     "start_time": "2020-09-06T02:57:43.331042Z"
    }
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "[[0 1 2]\n",
      " [3 4 5]\n",
      " [6 7 8]]\n",
      "[[3 4 5]\n",
      " [0 1 2]\n",
      " [6 7 8]]\n"
     ]
    }
   ],
   "source": [
    "import numpy as np\n",
    "\n",
    "arr = np.arange(9).reshape(3, 3)\n",
    "print(arr)\n",
    "# [[0 1 2]\n",
    "#  [3 4 5]\n",
    "#  [6 7 8]]\n",
    "\n",
    "x = arr[[1, 0, 2], :]\n",
    "print(x)\n",
    "# [[3 4 5]\n",
    "#  [0 1 2]\n",
    "#  [6 7 8]]"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "ExecuteTime": {
     "end_time": "2020-09-06T02:58:04.059418Z",
     "start_time": "2020-09-06T02:58:04.054430Z"
    }
   },
   "source": [
    "**反转二维数组arr的行。**\n",
    "\n",
    "- `arr = np.arange(9).reshape(3, 3)`\n",
    "\n",
    "【知识点：索引与切片】\n",
    "- 如何反转二维数组的行？"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
   "metadata": {
    "ExecuteTime": {
     "end_time": "2020-09-06T02:58:21.071694Z",
     "start_time": "2020-09-06T02:58:21.067682Z"
    }
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "[[0 1 2]\n",
      " [3 4 5]\n",
      " [6 7 8]]\n",
      "[[6 7 8]\n",
      " [3 4 5]\n",
      " [0 1 2]]\n"
     ]
    }
   ],
   "source": [
    "import numpy as np\n",
    "\n",
    "arr = np.arange(9).reshape(3, 3)\n",
    "print(arr)\n",
    "# [[0 1 2]\n",
    "#  [3 4 5]\n",
    "#  [6 7 8]]\n",
    "\n",
    "x = arr[::-1, :]\n",
    "print(x)\n",
    "# [[6 7 8]\n",
    "#  [3 4 5]\n",
    "#  [0 1 2]]"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "ExecuteTime": {
     "end_time": "2020-09-06T02:58:39.880250Z",
     "start_time": "2020-09-06T02:58:39.875230Z"
    }
   },
   "source": [
    "**反转二维数组arr的列。**\n",
    "- `arr = np.arange(9).reshape(3, 3)`\n",
    "\n",
    "【知识点：索引与切片】\n",
    "- 如何反转二维数组的列？"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 7,
   "metadata": {
    "ExecuteTime": {
     "end_time": "2020-09-06T02:58:54.851622Z",
     "start_time": "2020-09-06T02:58:54.846601Z"
    }
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "[[0 1 2]\n",
      " [3 4 5]\n",
      " [6 7 8]]\n",
      "[[2 1 0]\n",
      " [5 4 3]\n",
      " [8 7 6]]\n"
     ]
    }
   ],
   "source": [
    "import numpy as np\n",
    "\n",
    "arr = np.arange(9).reshape(3, 3)\n",
    "print(arr)\n",
    "# [[0 1 2]\n",
    "#  [3 4 5]\n",
    "#  [6 7 8]]\n",
    "\n",
    "x = arr[:, ::-1]\n",
    "print(x)\n",
    "# [[2 1 0]\n",
    "#  [5 4 3]\n",
    "#  [8 7 6]]"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": []
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